Droplet merging is a well established subject of investigation in classical fluids as it arises in different fundamental and practical
contexts.[1]}, [2]}, [3]}, [4]}, [5]} It involves viscous droplets, mostly drawn
together by surface tension or Van der Waals mutual attraction.
Experiments and models aim at determining e.g. how the radius of the contact region between drops grows as
a function of time after contact, or the final outcome of the interaction between two droplets
(merging in one single droplet or separation into two or several), which depends on the size, viscosity,
morphology and relative velocity of the colliding droplets, see e.g. Refs. Qia97,Men01,Pan05,Pan09,Hua19 and
references therein.
